I don't think that is necessarily what is occurring here. I'm not trying to defend subjective listening tests, but for "measurements" to be useful in assessing anything one has to be measuring the "right" things....
1. Comparison of USB power coming out of my computer compared to what comes out of these devices.
2. Noise floor of the analog output of the DAC to see it has gone done as a result of filtering and or regeneration of the bus.
3. Level of spurious distortions and noise when playing a 12 Khz signal.
Please explain why these are not useful or "right."
, one has to be measuring them in a repeatable and meaningful manner and one has to be able to interpret the measurements correctly.
As for interpretation, I did that too. I explained that while these products seemed to have degraded measured performance some, I consider them to do nothing audibly. Happy to see someone challenge me and explain otherwise. That is what we ultimately want, right? Whether measurements back output of the DAC changing?
Many posters are pointing out that in this case none of those requirements have been met.
What was repeatable about JohnW's measurements? Do you know what computer he used? What USB port? What cable? Nothing, right? I provided all of this detail.
And I'll repeat again, there is nothing "scientific" about this forum so far; no scientists have participated and no accepted scientific method is being used. If you want to be honest call it the "measurement forum", but also be honest about the breadth and depth of ignorance present.